Barrier material comprising a thermoplastic and a compatible cyclodextrin derivative

ABSTRACT

A barrier film composition can comprise a thermoplastic web comprising a thermoplastic polymer and a dispersed cyclodextrin composition having substituents that compatibilize the cyclodextrin in the film. The thermoplastic/cyclodextrin film obtains substantial barrier properties from the interaction between the substituted cyclodextrin in the film material with a permeant. The substituents on the cyclodextrin molecule causes the cyclodextrin to be dispersible and stable in the film material resulting in an extrudable thermoplastic. Such materials can be used as a single layer film material, a multilayer film material which can be coated or uncoated and can be used in structural materials wherein the thermoplastic is of substantial thickness resulting in structural stiffness. The cooperation between the cyclodextrin and the thermoplastic polymer provides barrier properties to a web wherein a permeant can be complexed or entrapped by the cyclodextrin compound and held within the film preventing the permeant from passing through the film into the interior of a film, an enclosure or container. The permeant can comprise a variety of well known materials such as moisture, aliphatic or aromatic hydrocarbons, monomer materials, off flavors, toxic compounds etc.

This is a division of application Ser. No. 08/264,771, filed Jun. 23,1994, now U.S. Pat. No. 5,492,947 which application is incorporatedherein by reference.

FIELD OF THE INVENTION

The invention relates to thermoplastic polymeric compositions used aspackaging materials with barrier properties. The thermoplastic barriermaterial can take the form of a barrier coating, a flexible film, asemi-rigid or rigid sheet or a rigid structure. The thermoplasticbarrier materials can also take the form of a coating manufactured froman aqueous or solvent based solution or suspension of thermoplastic filmforming components containing as one component, the barrier formingmaterials. Such a film sheet or coating material can act as a barrier toa variety of permeants including water vapor; organics such as aliphaticand aromatic hydrocarbons, aliphatic and aromatic halides, heterocyclichydrocarbons, alcohols, aldehydes, amines, carboxylic acids, ketones,ethers, esters, sulfides, thiols, monomers, etc.; off flavors and offodors, etc. The thermoplastic barrier compositions of the invention canbe extruded, laminated or molded into a variety of useful films, sheets,structures or shapes using conventional processing technology. Further,the monolayer, bilayer or multilayer films can be coated, printed orembossed.

BACKGROUND OF THE INVENTION

Much attention has been directed to the development of packagingmaterials in a film, a semi-rigid or rigid sheet and a rigid containermade of a thermoplastic composition. In such applications, the polymericcomposition preferably acts as a barrier to the passage of a variety ofpermeant compositions to prevent contact between, e.g., the contents ofa package and the permeant. Improving barrier properties is an importantgoal for manufacturers of film and thermoplastic resins.

Barrier properties arise from both the structure and the composition ofthe material. The order of the structure (i.e.,), the crystallinity orthe amorphous nature of the material, the existence of layers orcoatings can affect barrier properties. The barrier property of manymaterials can be increased by using liquid crystal or self-orderingmolecular technology, by axially orienting materials such as an ethylenevinyl alcohol film, or by biaxially orienting nylon films and by usingother useful structures. Internal polymeric structure can becrystallized or ordered in a way to increase the resistance topermeation of a permeant. A material can be selected, for thethermoplastic or packing coating, which prevents absorption of apermeant onto the barrier surface. The material can also be selected toprevent the transport of the permeant through the barrier. Permeationthat corresponds to Fick's law and non-Fickian diffusion has beenobserved. Generally, permeation is concentration and temperaturedependent regarding mode of transport.

The permeation process can be described as a multistep event. First,collision of the permeant molecule with the polymer is followed bysorption into the polymer. Next, migration through the polymer matrix byrandom hops occurs and finally the desorption of the penetrant from thepolymer completes the process. The process occurs to eliminate anexisting chemical concentration difference between the outside of thefilm and the inside of the package. Permeability of an organic moleculethrough a packaging film consists of two component parts, the diffusionrate and solubility of the molecule in the film. The diffusion ratemeasures how fast molecule transport occurs through the film. It affectsthe ease with which a permeant molecule moves within a-polymer.Solubility is a measure of the concentration of the permeant moleculethat will be in position to migrate through the film. Diffusion andsolubility are important measurements of a barrier film's performance.There are two types of mechanisms of mass transfer for organic vaporspermeating through packaging films: capillary flow and activateddiffusion. Capillary flow involves small molecules permeating throughpinholes or highly porous media. This is of course an undesirablefeature in a high barrier film. The second, called activated diffusion,consists of solubilization of the penetrants into an effectivelynon-porous film at the inflow surface, diffusion through the film undera concentration gradient (high concentration to low concentration), andrelease from the outflow surface at a lower concentration. In non-porouspolymeric films, therefore, the mass transport of a penetrant includesthree steps--sorption, diffusion, and desorption. Sorption anddesorption depend upon the solubility of the penetrant in the film. Theprocess of sorption of a vapor by a polymer can be considered to involvetwo stages: condensation of the vapor onto the polymer followed bysolution of the condensed vapor into the polymer. For a thin-filmpolymer, permeation is the flow of a substance through a film under apermeant concentration gradient. The driving force for permeation isgiven as the pressure difference of the permeant across the film.Several factors determine the ability of a permeant molecule to permeatethrough a membrane: size, shape, and chemical nature of the permeant,physical and chemical properties of the polymer, and interactionsbetween the permeant and the polymer.

A permeant for this application means a material thaw can exist in theatmosphere at a substantial detectable concentration and can betransmitted through a known polymer material. A large variety ofpermeants are known. Such permeants include water vapor, aromatic andaliphatic hydrocarbons, monomer compositions and residues, off odors,off flavors, perfumes, smoke, pesticides, toxic materials, etc. Atypical barrier material comprises a single layer of polymer, a twolayer coextruded or laminated polymer film, a coated monolayer, bilayeror multilayer film having one or more coatings on a surface or bothsurfaces of the film or sheet.

The two most widely used barrier polymers for food packaging areethylene-vinyl alcohol copolymers (EVOH) ethylene vinyl acetatecopolymers (EVA) and polyvinylidene chloride (PVDC). Other usefulthermoplastics include ethylene acrylic materials including ethyleneacrylic acid, ethylene methacrylic acid, etc. Such polymers areavailable commercially and offer some resistance to permeation of gases,flavors, aromas, solvents and most chemicals. PVDC is also an excellentbarrier to moisture while EVOH offers very good processability andpermits substantial use of regrind materials. EVOH copolymer resins arecommonly used in a wide variety of grades having varying ethyleneconcentrations. As the ethylene content is reduced, the barrierproperties to gases, flavors and solvents increase. EVOH resins arecommonly used in coextrusions with polyolefins, nylon or polyethyleneterephthalate (PET) as a structural layer. Commercially, amorphous nylonresins are being promoted for monolayer bottles and films. Moderatebarrier polymer materials such as monolayer polyethylene terephthalate,polymethyl pentene or polyvinyl chloride films are available.

Substantial attention is now directed to a variety of technologies forthe improvement of barrier properties. The use of both physical barriersand active chemical barriers or traps in packaging materials are underactive investigation. In particular, attention has focused on use ofspecific copolymer and terpolymer materials, the use of specific polymeralloys, the use of improved coatings for barrier material such as silicametals, organometallics, and other strategies.

Another important barrier technology involves the use of oxygenabsorbers or scavengers that are used in polymeric coatings or in bulkpolymer materials. Metallic reducing agents such as ferrous compounds,powdered oxide or metallic platinum can be incorporated into barriersystems. These systems scavenge oxygen by converting it into a stableoxide within the film. Non-metallic oxygen scavengers have also beendeveloped and are intended to alleviate problems associated with metalor metallic tastes or odors. Such systems include compounds includingascorbic acid (vitamin C) and salts. A recent introduction involvesorganometallic molecules that have a natural affinity for oxygen. Suchmolecules absorb oxygen molecules into the interior polymer chemicalstructure removing oxygen from the internal or enclosed space ofpackaging materials.

Packaging scientists are continuing to develop new polymeric films,coated films, polymeric alloys, etc. using blends of materials to attainhigher barrier properties. Many of these systems have attained somedegree of utility but have failed to achieve substantial commercialsuccess due to a variety of factors including obtaining barrierperformance at low cost.

One problem that arises when searching for polymer blends or compoundedpolymeric materials, relates to the physical properties of the film.Films must retain substantial clarity, tensile strength, resistance topenetration, tear resistance, etc. to remain useful in packagingmaterials. Blending unlike materials into a thermoplastic before filmextrusion often results in a substantial reduction of film properties.Finding compatible polymer materials for polymer alloys, and compatibleadditives for polymeric materials typically require empiricaldemonstration of compatibility and does not follow a clearly developedtheory. However compatibility can be demonstrated by showing that thecompounded material obtains an improved barrier quality with littlereduction in clarity, processability, or structural properties usingconventional test methods. Accordingly, a substantial need exists fordevelopment of materials that can be incorporated into polymericmaterial to form a packaging thermoplastic having excellent barrierproperties without any substantial reduction in structural properties.

BRIEF DISCUSSION OF THE INVENTION

I have found that the barrier properties of a thermoplastic polymer canbe improved, without any important reduction in clarity, processabilityor structural properties, by forming a barrier layer with a dispersedcompatible cyclodextrin derivative in the polymer. I have developed twoembodiments. The first comprises a barrier made using the thermoplastictechnology containing the cyclodextrin derivative. The second, a coatingmade by casting a solution or suspension of a film forming polymer orpolymer forming material combined with the cyclodextrin derivative toform a barrier layer. The cyclodextrin molecule without a compatiblesubstituent group is not sufficiently compatible in the bulk material toresult in a clear useful barrier layer or packaging material. Thecompatible cyclodextrin derivative is a compound substantially free ofan inclusion complex. For this invention the term "substantially free ofan inclusion complex" means that the quantity of the dispersedcyclodextrin derivative in the film contains a large fraction havingcyclodextrin rings free of a permeant in the interior of thecyclodextrin molecule. The cyclodextrin compound will be added withoutcomplex, but some complexing can occur during manufacture from polymerdegradation or from inks or coatings components. The internal cavity ofthe cyclodextrin remains unoccupied by any complexed molecule.

The cyclodextrin derivative has a substituent group bonded to thecyclodextrin molecule that is compatible with the polymeric material.Cyclodextrin is a cyclic dextran molecule having six or more glucosemoieties in the molecule. Preferably, the cyclodextrin is anα-cyclodextrin (αCD), a β-cyclodextrin (βCD), a γ-cyclodextrin (γCD) ormixtures thereof. We have found that the derivatization of thecyclodextrin molecule is essential for forming a cyclodextrin materialthat can be effectively blended into the thermoplastic bulk polymermaterial with no loss in clarity, processability or structural orpackaging properties. The substituents on the cyclodextrin molecule areselected to possess a composition, structure and polarity to match thatof the polymer to ensure that the cyclodextrin is sufficientlycompatible in the polymer material. Further, a derivatized cyclodextrinis selected that can be blended into the thermoplastic polymer, formedinto film, semirigid or rigid sheet or other rigid structural materialsusing conventional thermoplastic manufacturing techniques. Lastly, wehave found that the cyclodextrin material can be used in forming suchthermoplastic barrier structures without any substantial reduction instructural properties.

The film can provide a trap or barrier to contaminant materials from thepolymer matrix and from the product storage and use environment.Thermoplastic polymers used in manufacturing packaging film materialsare typically products made by polymerizing monomers resulting fromrefinery processes. Any refinery stream used in polymerizationchemistry, contains residual monomer, trace level refinery hydrocarbons,catalyst and catalyst by-products as impurities in the polymer matrix.Further, the environment in which materials are packaged afterproduction, stored and used, often contain substantial proportions ofcontaminants that can permeate through a barrier film or sheet and cancontaminate food or other packaged items. Residual polymer volatiles arecomplexed by dispersing cyclodextrin into molten film polymer using anextruder. The residents time or mixing time of CD (cyclodextrin) andmolten polymer in the barrel of the extruder initiates the complexationof residual polymer volatiles. With environmental contaminants diffusingthrough the polymer, uncomplexed cyclodextrin dispersed in the polymeris believed to reside, not only between the polymer molecule chains, butin vaguely defined cavities between the polymer chains. As the permeantdiffuses through the polymer on a tortuous path, the uncomplexedcyclodextrin is available to complex permeant molecules as they diffusethrough the film. Some continual complexation and release of the sameguest between cyclodextrin molecules in the film is possible. In otherwords, the cyclodextrin dispersed in the film is complexing andreleasing. The diffusion rate may increase due to the number and size ofthe cavities caused by the presence of cyclodextrin. The modifiedcyclodextrin preferably has chemical properties that are compatible withthe polymer and are of a size and shape that does not adversely affectthe film's barrier property.

The beneficial effect of cyclodextrin over other high-barrier filmtechnologies is twofold. First, cyclodextrin has the ability to complexresidual organic volatile contaminants inherent in all polyethylene andpolypropylene packaging films. Secondly, cyclodextrin offers the uniqueability to complex permeants that may otherwise diffuse through thepackage film-improving product quality and safety.

Since all packaging films are permeable to organic vapors, measuring theamount that permeates through the film over time is an importantperformance measurement of a particular packaging film. The permeationprocess described above is fast for low-water-activity packaged foodproducts (crackers, cookies, cereals). The process of permeation can befaster or slower depending on the relative humidity outside the packageand the product's storage temperature. As the relative humidity outsidethe package increase, the pressure differential between the outside andinside the package is greater. The greater the differential and/or thehigher the temperature, the faster the organic permeants will diffusethrough the film. The method used to test the film samples in thisresearch used the worst case (60% relative humidity outside the packageand 0.25 water activity inside the package) shelf-life storageconditions to accelerate the outcome of the testing. The organicpermeant concentration used has been obtained from food productscontaminated by inks used in printing on packaging materials, adhesivesystems used in polymer or paper or foil laminations, or numerousenvironmental contaminants originating from gasoline, diesel fuel, paintsolvent, cleaning materials, product fragrance, food products, etc. Therelative humidity, water activity and permeant concentration have beenused to test numerous high-barrier films presently used in the industrytoday. The testing has effectively demonstrated performance differencesbetween various high-barrier films. Four test parameters are importantin the performance of the high barrier film. First is the time it takesthe permeant to begin diffusing through the package wall known as"lag-time", second, the rate the permeant diffuses through the film,third, the total amount of permeant that can pass through the film overa given time, and fourth, the effectiveness of the barrier to thepermeant challenge.

FIG. 1 is a graphical representation of the dimensions of thecyclodextrin molecule without derivatization. The α, β and γcyclodextrins are shown.

FIG. 2 is a schematic diagram of the extruder used to form the films setforth in Table I.

FIG. 3 is a diagram of a test device used in measuring the permeabilityof the films of the inventions.

We have also found that inclusion of the cyclodextrin derivatives in thethermoplastic materials of the invention can improve other properties ofthe film such as surface tension, static charge properties and otherproperties that improve the adaptability of this barrier material tocoating and printing. The cyclodextrin derivative materials can beincluded in a variety of a thermoplastic film and sheet.

DETAILED DESCRIPTION OF THE INVENTION Film

A film or a sheet is a flat unsupported section of a thermoplastic resinwhose thickness is much smaller than its width or length. Films aregenerally regarded as being 0.25 millimeters (mm) or less, typically0.01 to 20 mm thick. Sheet may range from about 0.25 mm to severalcentimeters (cm), typically 0.3 to 3 mm in thickness. Film or sheet canbe used alone or in combination with other sheet, fabric or structuralunits through lamination, coextrusion or coating. For the invention theterm "web" includes film, sheet, semi-rigid and rigid sheet and formedrigid units. Important properties include tensile strength, elongation,stiffness, tear strength and resistance; optical properties includinghaze, transparency; chemical resistance such as water absorption andtransmission of a variety of permeant materials including water vaporand other permeants; electrical properties such as dielectric constant;and permanence properties including shrinkage, cracking, weatherability,etc.

Thermoplastic materials can be formed into barrier film using a varietyof processes including blown thermoplastic extrusion, linear biaxiallyoriented film extrusion and by casting from molten thermoplastic resin,monomer or polymer (aqueous or organic solvent) dispersion. Thesemethods are well known manufacturing procedures. The characteristics inthe polymer thermoplastics that lead to successful barrier-filmformation are as follows. Skilled artisans manufacturing thermoplasticpolymers have learned to tailor the polymer material for thermoplasticprocessing and particular end use application by controlling molecularweight (the melt index has been selected by the thermoplastic industryas a measure of molecular weight--melt index is inversely proportionalto molecular weight, density and crystallinity). For blown thermoplasticextrusion polyolefins are such as LDPE (low density polyethylene), LLDPE(linear low density polyethylene), and HDPE (high density polyethylene)the most frequently used thermoplastic polymers, although polypropylene,nylon, nitriles, PETG (Polyetheylene terphthalate) and polycarbonate aresometimes used to make blown film. Polyolefins typically have a meltindex from 0.2 to 3 grams/10 mins., a density of about 0.910 to about0.940 grams/cc, and a weight average molecular weight that can rangefrom about 200,000 to 500,000. For biaxially oriented film extrusion thepolymer most often used are olefin based--chiefly polyethylene andpolypropylene (melt index from about 0.4 to 4 grams/10 mins. and anM_(w) (weight average molecular weight) of about 200,000 to 600,000).Polyesters and nylons can also be used. For casting, moltenthermoplastic resin or monomer dispersion are typically produced frompolyethylene or polypropylene. Occasionally, nylon, polyester and PVC(polyvinylchloride) are cast. For roll coating of aqueous based acrylicurethane and PVDC (polyvinyl chloride), etc. dispersions are polymerizedto an optimum crystallinity and molecular weight before coating.

A variety of thermoplastic materials are used in making film and sheetproducts. Such materials includepoly(acrylonitrile-co-butadiene-co-styrene) polymers, acrylic polymerssuch as the polymethylmethacrylate, poly-n-butyl acrylate,poly(ethylene-co-acrylic acid), poly(ethylene-co-methacrylate), etc.;cellophane, cellulosics including cellulose acetate, cellulose acetatepropionate, cellulose acetate butyrate and cellulose triacetate, etc.;fluoropolymers including polytetrafluoroethylene (teflon),poly(ethylene-co-tetrafluoroethylene) copolymers,(tetrafluoroethylene-co-propylene) copolymers, polyvinyl fluoridepolymers, etc., polyamides such as nylon 6, nylon 6,6, etc.;polycarbonates; polyesters such as poly(ethylene-coterephthalate),poly(ethylene-co-1,4-naphthalene dicarboxylate),poly(butylene-co-terephthalate); polyimide materials; polyethylenematerials including low density polyethylene; linear low densitypolyethylene, high density polyethylene, high molecular weight highdensity polyethylene, etc.; polypropylene, biaxially orientedpolypropylene; polystyrene, biaxially oriented polystyrene; vinyl filmsincluding polyvinyl chloride, (vinyl chloride-co-vinyl acetate)copolymers, polyvinylidene chloride, polyvinyl alcohol, (vinylchloride-co-vinylidene dichloride) copolymers, specialty films includingpolysulfone, polyphenylene sulfide, polyphenylene oxide, liquid crystalpolyesters, polyether ketones, polyvinylbutyrl, etc.

Film and sheet materials are commonly manufactured using thermoplastictechniques including melt extrusion, calendaring, solution casting, andchemical regeneration processes. In many manufacturing steps an axial ora biaxial orientation step is used. The majority of film and sheetmanufactured using melt extrusion techniques. In melt extrusion, thematerial is heated above its melting point in an extruder typicallyhaving an introduction section 27, a melt region 28 and an extrudersection 29. The melt is introduced to a slot die resulting in a thinflat profile that is rapidly quenched to solid state and oriented.Typically the hot polymer film after extrusion is rapidly chilled on aroll or drum or using an air stream. Ultimately, a quenching bath can beused. Thermoplastic materials can also be blown. The hot melt polymer isextruded in FIG. 2 in an annular die 22 in a tube form 21. The tube isinflated with air (see air inlet 26) to a diameter determined by thedesired film properties and by practical handling considerations. As thehot melt polymer emerges from the annular die, the extruded hot tube isexpanded by air to 1.2 or four (4) times its initial die diameter. Atthe same time the cooling air (see air flow 20) chills the web forming asolid extruded with a hollow circular cross section 21. The film tube iscollapsed within a V-shaped frame 23 and is nipped at the end of theframe (nip rolls 24) to trap air within the thus formed bubble. Rolls 24and 25 draw the film from the die maintaining a continuous production ofthe extruded tube. We have found that in the preparation of biaxiallyoriented film and in the production of blown thermoplastic film that themelt temperature and the die temperature are important in obtaining thepermeability or permeant transmission rates preferred for films of theinvention, to reduce melt fracture and to improve film uniformity(reduce surface defects). Referring to FIG. 2, the temperature of themelt at the melt region 28 should range from about 390°-420° F.,preferably 395°-415° F. The temperature of the extrusion die 29 shouldrange from about 400°-435° F., preferably 410°-430° F. The extrudedpolymer can be cooled using ambient water baths or ambient air. Theextruder can be operated at through put such that production rates canbe maintained but the polymer can be sufficiently heated to achieve themelt and die temperatures required. Production of the films of theinvention at these temperatures ensures that the cyclodextrin materialis fully compatible in the thermoplastic melt, is not degraded by thehigh temperatures and a clear compatible useful barrier film isproduced.

Often two thermoplastic materials are joined in a coextrusion process toproduce tailored film or sheet products adapted to a particular end use.One or more polymer types in two or more layers of melt are coextrudedin a coextrusion die to have a film with versatile properties dried fromboth layers. Layers of the different polymers or resins are combined byeither blending the materials in melt before extrusion or by parallelextrusion of the different thermoplastics. The melt flows laminarlythrough the die and onto a quenched drum. The film is processedconventionally and may be oriented after cooling. Films can contain avariety of additives such as antioxidants, heat stabilizers, UVstabilizers, slip agents, fillers, and anti-block agents.

The barrier layer of the invention can be made by casting an aqueousdispersion or solvent dispersion or solution of a film forming polymerand the cyclodextrin derivative. The aqueous or solvent based materialcan be formed by commonly available aqueous or solvent based processingof commercially available polymers, polymer dispersions, polymersolutions or both polymer and common aqueous or solvent processingtechnology. The cyclodextrin derivative material can be combined withsuch aqueous or solvent based dispersions or solutions to form a filmforming or readily formed coating material. Such barrier layers orbarrier coatings can be formed using commonly available coatingtechnology including roller coating, doctor blade coating, spin coating,etc. While the coatings can be made and removed from a preparativesurface, commonly coatings are formed on a thermoplastic orthermosetting polymer Web, and remain in place to act as a barrier layeron a polymeric web used in a packaging. The typical coatings can be madefrom the same thermoplastic polymer materials used in film sheet orother structural layers using substantially similar loadings of thecyclodextrin derivative material. The barrier layer or barriercoatings-formed using the film forming polymer and the cyclodextrinderivative can be used as a single coating layer or can be used in amultiple coating structure having a barrier layer or coating on one orboth sides of a structural film or sheet which can be used with othercoating layers including printing layers, clear coating layers and otherlayers conventional in packaging, food packaging, consumer productpackaging, etc.

Cyclodextrin

The thermoplastic films of the invention contain a cyclodextrin havingpendent moieties or substituents that render the cyclodextrin materialcompatible with the thermoplastic polymer. For this invention,compatible means that the cyclodextrin material can be uniformlydispersed into the melt polymer, can retain the ability to trap orcomplex permeant materials or polymer impurity, and can reside in thepolymer without substantial reductions in polymer film characteristics.Compatibility can be determined by measuring polymer characteristicssuch as tensile strength, tear resistance, etc., permeability ortransmission rates for permeants, surface smoothness, clarity, etc.Non-compatible derivatives will result in substantial reduced polymerproperties, very high permeability or transmission rates and rough dullfilm. Qualitative compatibility screening can be obtained by preparingsmall batches (100 grams-one kilogram of thermoplastic and substitutedcyclodextrin). The blended material is extruded at productiontemperatures as a linear strand extrudate having a diameter of about oneto five mm. Incompatible cyclodextrin materials will not disperseuniformly-in the melt and can be seen in the transparent melt polymerimmediately upon extrusion from the extrusion head. We have found theincompatible cyclodextrin can degrade at extrusion temperatures andproduce a characteristic "burnt flour" odor in an extrusion. Further, wehave found that incompatible cyclodextrin can cause substantial meltfracture in the extrudate which can be detected by visual inspection.Lastly, the extrudate can be cut into small pieces, cross-sectioned andexamined using an optical microscope to find incompatible cyclodextrinclearly visible in the thermoplastic matrix.

Cyclodextrin is a cyclic oligosaccharide consisting of at least sixglucopyranose units joined by α(1→4) linkages. Although cyclodextrinwith up to twelve glucose residues are known, the three most commonhomologs (α cyclodextrin, β cyclodextrin and γ cyclodextrin) having 6, 7and 8 residues have been used.

Cyclodextrin is produced by a highly selective enzymatic synthesis. Theyconsist of six, seven, or eight glucose monomers arranged in a donutshaped ring, which are denoted α, β, or γ cyclodextrin respectively (SeeFIG. 1). The specific coupling of the glucose monomers gives thecyclodextrin a rigid, truncated conical molecular structure with ahollow interior of a specific volume. This internal cavity, which islipophilic (i.e.,) is attractive to hydrocarbon materials (in aqueoussystems is hydrophobic) when compared to the exterior, is a keystructural feature of the cyclodextrin, providing the ability to complexmolecules (e.g., aromatics, alcohols, halides and hydrogen halides,carboxylic acids and their esters, etc.). The complexed molecule mustsatisfy the size criterion of fitting at least partially into thecyclodextrin internal cavity, resulting in an inclusion complex.

    ______________________________________                                        CYCLODEXTRIN TYPICAL PROPERTIES                                               PROPERTIES    CD     α-CD                                                                             β-CD                                                                            γ-CD                               ______________________________________                                        Degree of            6        7      8                                        Polymerization                                                                (n =  )                                                                       Molecular Size (A°)                                                    inside diameter      5.7      7.8    9.5                                      outside diameter     13.7     15.3   16.9                                     height               7.0      7.0    7.0                                      Specific Rotation [α].sup.25 .sub.D                                                          +150.5   +162.5 +177.4                                   Color of iodine      Blue     Yellow Yellowish                                complex                              Brown                                    Solubility in water                                                           (g/100 ml) 25° C.                                                      Distilled Water      14.50    1.85   23.20                                    ______________________________________                                    

The oligosaccharide ring forms a torus, as a truncated cone, withprimary hydroxyl groups of each glucose residue lying on a narrow end ofthe torus. The secondary glucopyranose hydroxyl groups are located onthe wide end. The parent cyclodextrin molecule, and useful derivatives,can be represented by the following formula (the ring carbons showconventional numbering) in which the vacant bonds represent the balanceof the cyclic molecule: ##STR1## wherein R₁ and R₂ are primary orsecondary hydroxyl as shown.

Cyclodextrin molecules have available for reaction with a chemicalreagent the primary hydroxyl at the six position, of the glucose moiety,and at the secondary hydroxyl in the two and three position. Because ofthe geometry of the cyclodextrin molecule, and the chemistry of the ringsubstituents, all hydroxyl groups are not equal in reactivity. However,with care and effective reaction conditions, the cyclodextrin moleculecan be reacted to obtain a derivatized molecule having all hydroxylgroups derivatized with a single substituent type. Such a derivative isa persubstituted cyclodextrin. Cyclodextrin with selected substituents(i.e.) substituted only on the primary hydroxyl or selectivelysubstituted only at one or both the secondary hydroxyl groups can alsobe synthesized if desired. Further directed synthesis of a derivatizedmolecule with two different substituents or three different substituentsis also possible. These substituents can be placed at random or directedto a specific hydroxyl. For the purposes of this invention, thecyclodextrin molecule needs to contain sufficient thermoplasticcompatible substituent groups on the molecule to insure that thecyclodextrin material can be uniformly dispersed into the thermoplasticand when formed into a clear film, sheet or rigid structure, does notdetract from the polymer physical properties.

Apart from the introduction of substituent groups on the CD hydroxylother molecule modifications can be used. Other carbohydrate moleculescan be incorporated into the cyclic backbone of the cyclodextrinmolecule. The primary hydroxyl can be replaced using SN₂ displacement,oxidized dialdehyde or acid groups can be formed for further reactionwith derivatizing groups, etc. The secondary hydroxyls can be reactedand removed leaving an unsaturated group to which can be added a varietyof known reagents that can add or cross a double bond to form aderivatized molecule.

Further, one or more ring oxygen of the glycan moiety can be opened toproduce a reactive site. These techniques and others can be used tointroduce compatibilizing substituent groups on the cyclodextrinmolecule.

The preferred preparatory scheme for producing a derivatizedcyclodextrin material having a functional group compatible with thethermoplastic polymer involves reactions at the primary or secondaryhydroxyls of the cyclodextrin molecule. Broadly we have found that abroad range of pendant substituent moieties can be used on the molecule.These derivatized cyclodextrin molecules can include acylatedcyclodextrin, alkylated cyclodextrin, cyclodextrin esters such astosylates, mesylate and other related sulfo derivatives,hydrocarbyl-amino cyclodextrin, alkyl phosphono and alkyl phosphatocyclodextrin, imidazoyl substituted cyclodextrin, pyridine substitutedcyclodextrin, hydrocarbyl sulphur containing functional groupcyclodextrin, silicon-containing functional group substitutedcyclodextrin, carbonate and carbonate substituted cyclodextrin,carboxylic acid and related substituted cyclodextrin and others. Thesubstituent moiety must include a-region that provides compatibility tothe derivatized material.

Acyl groups that can be used as compatibilizing functional groupsinclude acetyl, propionyl, butyryl, trifluoroacetyl, benzoyl, acryloyland other well known groups. The formation of such groups on either theprimary or secondary ring hydroxyls of the cyclodextrin molecule involvewell known reactions. The acylation reaction can be conducted using theappropriate acid anhydride, acid chloride, and well known syntheticprotocols. Peracylated cyclodextrin can be made. Further, cyclodextrinhaving less than all of available hydroxyls substituted with such groupscan be made with one or more of the balance of the available hydroxylssubstituted with other functional groups.

Cyclodextrin materials can also be reacted with alkylating agents toproduced an alkylated cyclodextrin. Alkylating groups can be used toproduce peralkylated cyclodextrin using sufficient reaction conditionsexhaustively react available hydroxyl groups with the alkylating agent.Further, depending on the alkylating agent, the cyclodextrin moleculeused in the reaction conditions, cyclodextrin substituted at less thanall of the available hydroxyls can be produced. Typical examples ofalkyl groups useful in forming the alkylated cyclodextrin includemethyl, propyl, benzyl, isopropyl, tertiary butyl, allyl, trityl,alkyl-benzyl and other common alkyl groups. Such alkyl groups can bemade using conventional preparatory methods, such as reacting thehydroxyl group under appropriate conditions with an alkyl halide, orwith an alkylating alkyl sulfate reactant.

Tosyl(4-methylbenzene sulfonyl) mesyl (methane sulfonyl) or otherrelated alkyl or aryl sulfonyl forming reagents can be used inmanufacturing compatibilized cyclodextrin molecules for use inthermoplastic resins. The primary --OH groups of the cyclodextrinmolecules are more readily reacted than the secondary groups. However,the molecule can be substituted on virtually any position to form usefulcompositions.

Such sulfonyl containing functional groups can be used to derivatizeeither of the secondary hydroxyl groups or the primary hydroxyl group ofany of the glucose moieties in the cyclodextrin molecule. The reactionscan be conducted using a sulfonyl chloride reactant that can effectivelyreact with either primary or secondary hydroxyl. The sulfonyl chlorideis used at appropriate mole ratios depending on the number of targethydroxyl groups in the molecule requiring substitution. Both symmetrical(per substituted compounds with a single sulfonyl moiety) orunsymmetrical (the primary and secondary hydroxyls substituted with amixture of groups including sulfonyl derivatives) can be prepared usingknown reaction conditions. Sulfonyl groups-can be combined with acyl oralkyl groups generically as selected by the experimenter. Lastly,monosubstituted cyclodextrin can be made wherein a single glucose moietyin the ring contains between one and three sulfonyl substituents. Thebalance of the cyclodextrin molecule remaining unreacted.

Amino and other azido derivatives of cyclodextrin having pendentthermoplastic polymer containing moieties can be used in the sheet, filmor container of the invention. The sulfonyl derivatized cyclodextrinmolecule can be used to generate the amino derivative from the sulfonylgroup substituted cyclodextrin molecule via nucleophilic displacement ofthe sulfonate group by an azide (N₃ ⁻¹) ion. The azido derivatives aresubsequently converted into substituted amino compounds by reduction.Large numbers of these azido or amino cyclodextrin derivatives have beenmanufactured. Such derivatives can be manufactured in symmetricalsubstituted amine groups (those derivatives with two or more amino orazido groups symmetrically disposed on the cyclodextrin skeleton or as asymmetrically-substituted amine or azide derivatized cyclodextrinmolecule. Due to the nucleophilic displacement reaction that producesthe nitrogen containing groups, the primary hydroxyl group at the6-carbon atom is the most likely site for introduction of a nitrogencontaining group. Examples of nitrogen containing groups that can beuseful in the invention include acetylamino groups (--NHAc), alkylaminoincluding methylamino, ethylamino, butylamino, isobutylamino,isopropylamino, hexylamino, and other alkylamino substituents. The aminoor alkylamino substituents can further be reactive with other compoundsthat react with the nitrogen atom to further derivatize the amine group.Other possible nitrogen containing substituents include dialkylaminosuch as dimethylamino, diethylamino, piperidino, piperizino, quaternarysubstituted alkyl or aryl ammonium chloride substituents, halogenderivatives of cyclodextrins can be manufactured as a feed stock for themanufacture of a cyclodextrin molecule substituted with acompatibilizing derivative. In such compounds the primary or secondaryhydroxyl groups are substituted with a halogen group such as fluoro,chloro, bromo, iodo or other substituents. The most likely position forhalogen substitution is the primary hydroxyl at the 6-position.

Hydrocarbyl substituted phosphono or hydrocarbyl substituted phosphatogroups can be used to introduce compatible derivatives onto thecyclodextrin. At the primary hydroxyl, the cyclodextrin molecule can besubstituted with alkyl phosphato, aryl phosphato groups. The 2, and 3,secondary hydroxyls can be branched using an alkyl phosphato group.

The cyclodextrin molecule can be substituted with heterocyclic nucleiincluding pendent imidazole groups, histidine, imidazole groups,pyridino and substituted pyridino groups.

Cyclodextrin derivatives can be modified with sulfur containingfunctional groups to introduce compatibilizing substituents onto thecyclodextrin. Apart from the sulfonyl acylating groups found above,sulfur containing groups manufactured based on sulfhydryl chemistry canbe used to derivatize cyclodextrin. Such sulfur containing groupsinclude methylthio (--SMe), propylthio (--SPr), t-butylthio(--S--C(CH₃)₃), hydroxyethylthio (--S--CH₂ CH₂ OH),imidazolylmethylthio, phenylthio, substituted phenylthio, aminoalkylthioand others. Based on the ether or thioether chemistry set forth above,cyclodextrin having substituents ending with a hydroxyl aldehyde ketoneor carboxylic acid functionality can be prepared. Such groups includehydroxyethyl, 3-hydroxypropyl, methyloxylethyl and corresponding oxemeisomers, formyl methyl and its oxeme isomers, carbylmethoxy (--O--CH₂--CO₂ H), carbylmethoxymethyl ester (--O--CH₂ C₂ --CH₃). Cyclodextrinwith derivatives formed using silicone chemistry can containcompatibilizing functional groups.

Cyclodextrin derivatives with functional groups containing silicone canbe prepared. Silicone groups generally refer to groups with a singlesubstituted silicon atom or a repeating silicone-oxygen backbone withsubstituent groups. Typically, a significantly proportion of siliconeatoms in the silicone substituent bear hydrocarbyl (alkyl or aryl)substituents. Silicone substituted materials generally have increasedthermal and oxidative stability and chemical inertness. Further, thesilicone groups increase resistance to weathering, add dielectricstrength and improve surface tension. The molecular structure of thesilicone group can be varied because the silicone group can have asingle silicon atom or two to twenty silicon atoms in the siliconemoiety, can be linear or branched, have a large number of repeatingsilicone-oxygen groups and can be further substituted with a variety offunctional groups. For the purposes of this invention the simplesilicone containing substituent moieties are preferred includingtrimethylsilyl, mixed methyl-phenyl silyl groups, etc. We are aware thatcertain βCD and acetylated and hydroxy alkyl derivatives are availablefrom American Maize-Products Co., Corn Processing Division, Hammond,Ind.

Packages and Packed Items

The thermoplastic containing the compatible derivatized cyclodextrin canbe used in a variety of packaging formats to package a variety of items.General packaging ideas can be used. For example, the items can bepackaged entirely in a film pouch, bag, etc. Further, the film can beused as a film closure on a rigid plastic container. Such containers canhave a rectangular, circular, square or other shaped cross-section, aflat bottom and an open top. The container and a thermoplastic filmclosure can be made of the thermoplastic materials of the invention.Further, the thermoplastics of the invention can be used in theformation of blister pack packaging, clam shell type enclosures, tub,tray, etc. Generally, two product types require packaging inthermoplastic film of the invention having substantial barrierproperties. In one product type, protecting the product fromcontamination from permeant sources outside the packaging material isimportant. Protecting food items from contamination by aromatic andaliphatic hydrocarbons, fluorocarbons, ink and packaging residue,exhaust from transportation equivalent and other internal combustionengines, perfumes commonly used in a variety of consumer products suchas scented paper products, bar soap, scented bath products, cleaners,fabric softeners, detergents, dry bleaches, disinfectants, etc. All fooditems are the most common material requiring protection from outsidecontamination, other items can be sensitive to odors. Further, a varietyof materials must be packaged in barrier materials preventing the odorof the material from exiting the package. A large variety of food odorsare readily transmitted by a variety of packaging materials. Such foododors can attract insect and rodent pests, can be objectionable tocustomers or employees or can result in the substantial loss ofimportant fragrance notes from packaged materials reducing productvalue. Important odors requiring substantial barriers include odorsderived from coffee, ready to eat cereal, frozen pizza, cocoa or otherchocolate products, dry mix gravies and soups, snack foods (chips,crackers, popcorn, etc.), baked foods, dry pet food (cat food, etc.),butter or butter-flavor notes, meat products, in particular butter orbutter-flavor notes used in the manufacture of microwave popcorn inmicrowaveable paper containers, fruits and nuts, etc.

The above explanation of the nature of the cyclodextrin derivatives,thermoplastic films, manufacturing detail regarding the production offilm, and the processes of cyclodextrin to make compatible derivativesprovides a basis for understanding technology involving incorporatingcompatible cyclodextrin in thermoplastic film for barrier purposes. Thefollowing examples, film preparation and permeation data provide afurther basis for understanding the invention and includes the bestmode.

After our work in producing derivatives of cyclodextrins and compoundingthe cyclodextrins in thermoplastic films, we have found that thecyclodextrins can be readily derivatized using a variety of knownchemical protocols. The cyclodextrin material can be melt blended intothermoplastic materials smoothly resulting in clear extrudablethermoplastic materials with the cyclodextrin materials uniformlydistributed throughout the thermoplastic. Further, we have found thatthe cyclodextrin derivatives can be combined with a broad variety ofthermoplastic films. The cyclodextrin materials can be incorporated intothe films in a broad range of cyclodextrin concentrations. Thecyclodextrin containing thermoplastic materials can be blown into filmsof varying thickness and can be blown free of melt fracture or otherfilm or sheet variation. We have found in our experimentation that thebarrier properties, i.e. reduction in transmission rate of aromatichydrocarbons, aliphatic hydrocarbons, ethanol and water vapor can beachieved using the cyclodextrin derivative technology. We have alsofound that the use of cyclodextrin materials improve the surfaceproperties of the film. The surface tension of the film surface andsurface electrical properties were also improved. Such a resultincreases the utility of the films of the invention in coating,printing, laminating, handling, etc. In initial work we have also found(1) several modified cyclodextrin candidates were found to be compatiblewith the LLDPE resin and provide good complexation of residual LLDPEvolatile contaminants as well as reduce organic permeants diffusingthrough the film. (2) Unmodified βCD adversely affects transparency,thermal stability, machinability, and barrier properties of the film.Conversely, selected modified βCD (acetylated and trimethylsilyl etherderivatives) have no affect on transparency and thermal stability. Themachinability of the extruded plastic material is effected somewhatcausing some surface defects, thereby reducing the barrier properties ofthe film. (3) Films containing a modified βCD composition (1% by weight)reduce aromatic permeants by 35% at 72° F. and 38% at 105° F.; aliphaticpermeants were reduced by only 9% at 72° F. These results would improvesignificantly if worst case shelf-life testing conditions were not usedto test the films. (4) Complexation rates were different for aromaticand aliphatic permeants. Films containing modified βCD had bettercomplexation rates for aromatics (gasoline-type compounds) thanaliphatic (printing ink-type compounds). Conversely, film coating hadsignificantly better complexation of aliphatic compound than aromaticcompounds. (5) βCD containing acrylic coatings were the star performersreducing aliphatic permeants from 46% to 88%, while aromatics werereduced by 29%.

QUALITATIVE PREPARATION

Initially, we produced four experimental test films. Three of the filmscontained β-cyclodextrin βCD at loading of 1%, 3% and 5% (wt./wt.) whilethe fourth was a control film made from the same batch of resin andadditives but without βCD. The 5% loaded βCD film was tested forcomplexation of residual organic in the test film. Even though βCD wasfound to effectively complex residual organics in the linear low densitypolyethylene (LLDPE) resin, it was incompatible with the resin andformed βCD particle agglomerations.

We have evaluated nine modified βcyclodextrins and a milledβ-cyclodextrin (particle size 5 to 20 microns). The differentcyclodextrin modifications were acetylated, octanyl succinate,ethoxyhexyl glycidyl ether, quaternary amine, tertiary amine,carboxymethyl, succinylated, amphoteric and trimethylsilyl ether. Eachexperimental cyclodextrin (1% loading wt/wt) was mixed with low densitypolyethylene (LLDPE) using a Littleford mixer and then extruded using atwin screw Brabender extruder.

The nine modified cyclodextrin and milled cyclodextrin LLDPE profileswere examined under an optical microscope at 50× and 200× magnification.The microscopic examination was used to visually check for compatibilitybetween LLDPE resin and cyclodextrin. Of the ten cyclodextrin candidatestested, three (acetylated, octanyl succinate and trimethylsilyl ether)were found visually to be compatible with the LLDPE resin.

Complexed residual film volatiles were measured using cryotrappingprocedure to test 5% βCD film sample and three extruded profilescontaining 1% (wt/wt) acetylated βCD octanyl succinate βCD andtrimethylsilyl ether. The method consists of three separate steps; thefirst two are carried out simultaneously while the third, aninstrumental technique for separating and detecting volatile organiccompounds, is conducted after one and two. In the first step, an inertpure, dry gas is used to strip volatiles from the sample. During the gasstripping step, the sample is heated at 120° C. The sample is spikedwith a surrogate (benzene-d6) immediately prior to the analysis.Benzene-d₆ serves as an internal QC surrogate to correct each set oftest data for recovery. The second step concentrates the volatilesremoved from the sample by freezing the compounds from the stripping gasin a headspace vial immersed in a liquid nitrogen trap. At the end ofthe gas-stripping step, an internal standard (toluene-d8) is injecteddirectly into the headspace vial and the vial is capped immediately.Method and system blanks are interspersed with samples and treated inthe same manner as samples to monitor contamination. The concentratedorganic components are then separated, identified and quantitated byheated headspace high resolution gas chromatography/mass spectrometry(HRGC/MS). The results of the residual volatile analyses are presentedin the table below:

                  TABLE 1                                                         ______________________________________                                                           % Volatile Complexation                                    Sample Identification                                                                            as Compared to Control                                     ______________________________________                                        5% βCD Blown Film                                                                           80                                                         1% Acylated βCD Profile                                                                     47                                                         1% Octanyl Succinate βCD Profile                                                             0                                                         1% Trimethylsilyl ether Profile                                                                  48                                                         1% βCD Milled Profile                                                                       29                                                         ______________________________________                                    

In these preliminary screening tests, βCD derivatives were shown toeffectively complex trace volatile organics inherent in low densitypolyethylene resin used to make experimental film. In 5% βCD loadedLLDPE film, approximately 80% of the organic volatiles were complexed.However, all βCD films (1% and 5%) had an off-color (light brown) andoff-odor. The color and odor problem is believed to be the result ofdirect decomposition of the CD or impurity in the CD. Two odor-activecompounds (2-furaldehyde and 2-furanmethanol) were identified in theblown film samples.

Of the three modified compatible CD candidates (acetylated, octanylsuccinate and trimethylsilyl ether), the acetylated and trimethylsilylether CD were shown to effectively complex trace volatile organicsinherent in the LLDPE resin. One percent loadings of acetylated andtrimethylsilyl ether (TMSE) βCD showed approximately 50% of the residualLPDE organic volatiles were complexed, while the octanyl succinate CDdid not complex residual LLDPE resin volatiles. Milled βCD was found tobe less effective (28%) than the acetylated and TMSE modified βCD's.

Plastic packaging materials all interact to some degree with the foodproduct they protect. The main mode of interaction of plastic packagingof food is through the migration of organic molecules from theenvironment through the polymer film into the head space of the packagewhere they are absorbed by the food product. Migration or transfer oforganic molecules of the package to the food, during storage, iseffected by environmental conditions such as temperature, storage time,and other environmental factors (e.g., humidity, type of organicmolecules and concentration thereof). Migration can have both quality(consumer resistance) and toxicological influence. The objective ofpackaging film testing is to measure how specific barriers may influencethe quality of packaged individual foods. To simulated acceleratedshelf-life testing for low-water-activity food products, the testing wasconducted at a temperature of 72° F. and 105° F., and a relativehumidity of 60%. These temperature and humidity conditions are probablysimilar to those found in uncontrolled warehouses, in transit, and instorage.

If a polymer is moisture sensitive, the relative humidity can affect thefilm's performance especially in low-water-activity food products.Because a packaging film during actual end-use conditions will beseparating two moisture extremes, relative humidity in the permeationdevice was controlled on both sides of the film. The environment side,representing the outside of the package, was maintained at 60% relativehumidity, and the sample side, representing the inside of a packagecontaining a low-water-activity product, at 0.25.

A combination of permeants was used to measure the function andperformance of the CD. A combination was used to be realistic, sincegasoline (principally an aromatic hydrocarbon mixture) and printing inksolvents (principally an aliphatic hydrocarbon mixture) are not formedfrom a single compound but are a mixture of compounds.

The aromatic permeant contained ethanol (20 ppm), toluene (3 ppm),p-xylene (2 ppm), o-xylene (1 ppm), trimethyl-benzene (0.5 ppm) andnaphthalene (0.5 ppm). The aliphatic permeant, a commercial paintsolvent blend containing approximately twenty (20) individual compounds,was 20 ppm.

The permeation test device FIG. 3 consists of two glass permeation cellsor flasks with cavities of 1200 ml (environment cell or feed side) and300 ml (sample cell or permeating side).

Experimental film performance was measured in the closed-volumepermeation device. High-resolution gas chromatograph (HRGC) operatedwith a flame ionization detector (FID) was used to measure the change inthe cumulative penetrant concentration as a function of time.Sample-side (food product side) compound concentrations are calculatedfrom each compound's response factor. Concentrations are reported inparts per million (ppm) on a volume/volume basis. The cumulativepenetrant concentration on the sample-side of the film is plotted as afunction of time.

We produced four experimental test films. Three of the films containedβD at loading of 1%, 3% and 5% (wt/wt) while the fourth was a controlfilm made from the same batch of resin and additives but without βCD.

A second experimental technique was also undertaken to determine whetherβCD sandwiched between two control films will complex organic vaporspermeating the film. The experiment was carried out by lightly dustingβCD between two control film sheets.

The testing showed the control film performed better than βCD loadedfilms. The permeation test results also demonstrated the higher the βCDloading the poorer the film performed as a barrier. The test results forsandwiching βCD between two control films showed βCD being twice aseffective in reducing permeating vapors than the control samples withoutβCD. This experiment supported that CD does complex permeating organicvapors in the film if the film's barrier qualities are not changedduring the manufacturing process making the film a less effectivebarrier.

The 1% TMSE βCD film was slightly better than the 1% acetylated βCD film(24% -vs- 26%) for removing aromatic permeants at 72° F. adding moremodified CD appeared to have no improvement.

For aromatic permeants at 105° F., both 1% TMSE βCD and 1% acetylatedβCD are approximately 13% more effective removing aromatic permeantsthan 72° F. The 1% TMSE film was again slightly better than the 1% film(36% -vs- 31%) for removing aromatic permeants.

The 1% TMSE film was more effective initially removing aliphaticpermeants than the 1% acetylated βCD film at 72° F. But for the durationof the test, 1% TMSE βCD was worse than the control while 1% acetylatedβCD removed only 6% of the aliphatic permeants.

We produced two experimental aqueous coating solutions. One solutioncontained hydroxyethyl βCD (35% by weight) and the other solutioncontained hydroxypropyl βCD (35 by weight). Both solutions contained 10%of an acrylic emulsion comprising a dispersion of polyacrylic acidhaving an M_(w) (weight average molecular weight) of about 150,000(Polysciences, Inc.) (15% solids by weight) as a film forming adhesive.These solutions were used to hand-coat test film samples by laminatingtwo LLDPE films together. Two different coating techniques were used.The first technique very slightly stretched two film samples flat, thecoating was then applied using a hand roller, and then the films werelaminated together while stretched flat. The Rev. 1 samples were notstretched during the lamination process. All coated samples were finallyplaced in a vacuum laminating press to remove air bubbles between thefilm sheets. Film coating thicknesses were approximately 0.0005 inches.These CD coated films and hydroxylmethyl cellulose coated control filmswere subsequently tested.

A reduction in aromatic and aliphatic vapors by the hydroxyethyl βCDcoating is greater in the first several hours of exposure to the vaporand then diminishes over the next 20 hours of testing. Higher removal ofaliphatic vapors than aromatic vapors was achieved by the hydroxyethylβCD coating; this is believed to be a function of the difference intheir molecular size (i.e., aliphatic compounds are smaller thanaromatic compounds). Aliphatic permeants were reduced by 46% as comparedto the control over the 20 hour test period. Reduction of aromaticvapors was 29% as compared to the control over the 17 hour test period.

The Rev. 1 coated hydroxyethyl βCD reduced the aliphatic permeants by87% as compared to the control over the 20 hour test period. It is notknown if the method of coating the film was responsible for theadditional 41% reduction over the other hydroxyethyl βCD coated film.

The hydroxyethyl βCD coating was slightly better for removing aromaticpermeants than the hydroxypropyl βCD coating (29% -vs- 20%) at 72° F.

LARGE SCALE FILM EXPERIMENTAL Preparation of Cyclodextrin DerivativesEXAMPLE I

An acetylated β-cyclodextrin was obtained that contained 3.4 acetylgroups per cyclodextrin on the primary --OH group.

EXAMPLE II

Trimethyl Silyl Ether of β-cyclodextrin

Into a rotary evaporator equipped with a 4000 milliliter round bottomflask and a nitrogen atmosphere, introduced at a rate of 100 millilitersN₂ per minute, was placed three liters of dimethylformamide. Into thedimethylformamide was placed 750 grams of β-cyclodextrin. Theβ-cyclodextrin was rotated and dissolved in dimethylformamide at 60° C.After dissolution, the flask was removed from the rotary evaporator andthe contents were cooled to approximately 18° C. Into the flask, placedon a magnetic stirrer and equipped with a stir bar, was added 295milliliters of hexamethyldisilylazine (HMDS-Pierce Chemical No. 84769),followed by the careful addition of 97 milliliters oftrimethylchlorosilane (TMCS-Pierce Chemical No. 88531). The carefuladdition was achieved by a careful dropwise addition of an initialcharge of 20 milliliters and after reaction subsides the carefuldropwise addition of a subsequent 20 milliliter portions, etc. untiladdition is complete. After the addition of the TMCS was complete, andafter reaction subsides, the flask and its contents were placed on therotary evaporator, heated to 60° C. while maintaining an inert nitrogenatmosphere flow of 100 milliliters of N₂ per minute through the rotaryevaporator. The reaction was continued for four hours followed byremoval of solvent, leaving 308 grams of dry material. The material wasremoved from the flask by filtering, washing the filtrate with deionizedwater to remove the silylation products, vacuum oven drying (75° C. at0.3 inches of Hg) and stored as a powdered material and maintained forsubsequent compounding with a thermoplastic material. Subsequentspectrographic inspection of the material showed the β-cyclodextrin tocontain approximately 1.7 trimethylsilylether substituent perβ-cyclodextrin molecule. The substitution appeared to be commonly on aprimary 6-carbon atom.

EXAMPLE III

An hydroxypropyl β-cyclodextrin was obtained with 1.5 hydroxypropylgroups per molecule on the primary 6-OH group of the βCD.

EXAMPLE IV

An hydroxyethyl β-cyclodextrin was obtained with 1.5 hydroxyethyl groupsper molecule on the primary 6-OH group of the βCD.

Preparation of Films

We prepared a series of films using a linear low density polyethyleneresin, βCD and derivatized βCD such as the acetylated or thetrimethylsilyl derivative of a β-cyclodextrin. The polymer particleswere dry blended with the powdered β-cyclodextrin and β-cyclodextrinderivative material, a fluoropolymer lubricant (3M) and the antioxidantuntil uniform in the dry blend. The dry blend material was mixed andextruded in a pellet form in a Haake System 90, 3/4" conical extruder.The resulting pellets were collected for film preparation.

Table IA displays typical pelletizing extruder conditions. The filmswere blown in the apparatus of FIG. 2. FIG. 2 shows extrudedthermoplastic tube 21 exiting the die 22. The tube is collapsed by die23 and layered by rollers 24 into the film 25. The extruded tube 21 isinflated using air under pressure blown through air inlet tube 26. Thethermoplastic is melted in the extruder. The extruder temperature istaken at the mixing zone 27. The melt temperature is taken in the meltzone 28 while the die temperature is taken in the die 29. The extrudateis cooled using an air blown cooling stream from the cooling ring 20.The general schematic background of FIG. 2 is representative of theKiefel blown film extruder, 40 mm die diameter, used in the actualpreparation of the blown film. The film is manufactured according to theabove protocol and reported in Table IB. The film was tested fortransmission rates at a variety of environmental conditions.Environmental test conditions are shown below in Table II.

                  TABLE IA                                                        ______________________________________                                        0.5% TMSE Pelletizing 1-19-94                                                 ______________________________________                                        Run Time                                                                              0 min   Torque     4866    Rotor 198                                          13 sec  Tot. Torque                                                                              meter-gram                                                                            Aux.  rpm                                                             0.0           0%                                                              mkg-min                                            Channels                                                                               1       2       3    4    5   6                                      Melt Temp                                                                              37      41     41    41  41         °C.                       Set Temp                                                                              150     160     160  170   0   0     °C.                       Deviation                                                                              0       0       0    0    0   0     °C.                       Cooling Yes     Yes    Yes   Yes                                              Pressure                                                                               0       0     2739   0    0         psi                              ______________________________________                                    

                                      TABLE IB                                    __________________________________________________________________________    Extruded Films (Exxon LL3201)                                                 Made With Low Density Polyethylene                                            Roll     Fluoropolymer                                                                         Extruder Temp.                                                                        Melt  Die Temp.       Die                            No.                                                                              Sample ID                                                                           Additive.sup.1                                                                        Zone 3 (F.)                                                                           Temp (F.)                                                                           Zone 3 (F.)                                                                         Lbs./Hr                                                                             RPM Gap Comments                   __________________________________________________________________________    1  Control                                                                              500 ppm                                                                              428     406   406   30.1  50  24                             2  1% Ex. I                                                                            1000 ppm                                                                              441     415   420   29.7  50  35                             3  1% Ex. I                                                                            1000 ppm                                                                              441     416   420   28.5  50  35                             4  1% Ex. I                                                                             500 ppm                                                                              441     415   420   29.9  50  35                             5  1% Ex. I                                                                             500 ppm                                                                              418     405   414   29.9  50  35                             6  1% Ex. I                                                                             500 ppm                                                                              421     397   414   29.0  50  35                             7  0.5% Ex. I                                                                           500 ppm                                                                              421     403   415   29.0  50  35                             8  2% Ex. I                                                                             500 ppm                                                                              421     404   415   27.7  50  35  Very slight melt                                                              fracture                   9  1% Ex. II                                                                            500 ppm                                                                              421     406   415   28.3  50  35  Particles in film.         10 1% Ex. II                                                                            500 ppm                                                                              426     410   415   26.7  50  35  Particles in film.         11 1% Ex. II                                                                            500 ppm                                                                              432     415   414   29.0  50  35  Particles in film.                                                            Very                                                                          slight yellowing to                                                           film.                      12 1% Ex. II                                                                            500 ppm                                                                              431     414   415   21.5  39  35  Particles in film.         13 0.5% Ex. II                                                                          500 ppm                                                                              431     415   415   27.7  50  35  Particles in film.         14 0.5% Ex. II                                                                          500 ppm                                                                              425     410   415   28.9  50  35  Particles in film.         15 2% Ex. II                                                                            500 ppm                                                                              410     414   415   20.2  38  35  Particles in film.                                                            Very                                                                          slight yellowing to                                                           film.                      16 2% Ex. II                                                                            500 ppm                                                                              422     415   415   20.5  38  35  Particles in film.                                                            Very                                                                          slight yellowing to                                                           film.                      17 2% Ex. II                                                                            500 ppm                                                                              422     416   415   20.5  38  35  Particles in film.         __________________________________________________________________________                                                       Very                        .sup.1 Also contains 500 ppm Irganox 1010 antioxidant and 1000 ppm IrgaFo     168.                                                                     

                  TABLE II                                                        ______________________________________                                        Test Conditions                                                               Roll Sample                                                                            Temp.    Sample    Environ.                                          ID Number                                                                              (F.)     Side      Side                                              ______________________________________                                                                             Permeant.sup.2                           Roll #2  72       Rm % RH   Rm % RH  Aromatic/                                                                     Alcohol                                  Roll #3                                                                       Roll #5                                                                       Roll #6                                                                       Roll #5  72       Rm % RH   Rm % RH  Aromatic/                                                                     Alcohol                                  Roll #8                                                                       Roll #7  72       0.25 Aw   60% RH   Aromatic/                                                                     Alcohol                                  Roll #5                                                                       Roll #8                                                                       Roll #7  72       .60 Aw    30% RH   Aromatic/                                                                     Alcohol                                  Roll #5                                                                       Roll #8                                                                       Roll #2  105      Rm % RH   Rm % RH  Aromatic/                                                                     Alcohol                                  Roll #3                                                                       Roll #4                                                                       Roll #5                                                                       Roll #6                                                                       Roll #8                                                                       Roll #12                                                                      Roll #7  105      0.25 Aw   15% RH   Aromatic/                                                                     Alcohol                                  Roll #5                                                                       Roll #8                                                                       Roll #13 72       Rm % RH   Rm % RH  Aromatic/                                                                     Alcohol                                  Roll #14                                                                      Roll #9                                                                       Roll #9                                                                       Roll #11                                                                      Roll #12                                                                                                           Permeant.sup.34                          Roll #15                                                                      Roll #16                                                                      Roll #17                                                                      Roll #14 105      Rm % RH   Rm % RH  Aromatic/                                                                     Alcohol                                  Roll #15                                                                      10% Ex. III                                                                            72       0.25 Aw   60% RH   Aromatic/                                in PVdC                              Alcohol                                  20% Ex. III                                                                   in PVdC                                                                       5% Ex. III/                                                                            72       Rm % RH   Rm % RH  Aromatic/                                Acrylic                              Alcohol                                  10% Ex. III/                                                                  Acrylic                                                                       Roll #7  72       Rm % RH   Rm % RH  Naphtha                                  Roll #5                                                                       Roll #8                                                                       Roll #12 72       Rm % RH   Rm % RH  Naphtha                                  Roll #15                                                                      ______________________________________                                         .sup.2 7 ppm aromatic plus 20 ppm ETOH.                                       .sup.3 7 ppm aromatic plus 20 ppm ETOH.                                       .sup.4 40 ppm Naphtha                                                    

The results of the testing show that the inclusion of a compatiblecyclodextrin material in the thermoplastic films of the inventionsubstantially improves the barrier properties by reducing transmissionrate of a variety of permeants. The data showing the improvement intransmission rate is shown below in the following data tables.

    __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: Room % RH                                                        Environment: Room % RH                                                                         Aromatics %      Tot. Volitiles %                            Sample Aromatic  Improvement                                                                          Total Volitiles                                                                         Improvement                                 Identification                                                                       Transmission Rate*                                                                      Over Control                                                                         Transmission Rate*                                                                      Over Control                                __________________________________________________________________________    Control Film                                                                         3.35E-04   0%    3.79E-04   0%                                         1.0% CS-001                                                                          3.18E-04   5%    3.61E-04   5%                                         (Roll #2)                                                                     1.0% CS-001                                                                          2.01E-04  40%    2.55E-04  33%                                         (Roll #3)                                                                     1.0% CS-001                                                                          2.67E-04  20%    3.31E-04  13%                                         (Roll #5)                                                                     1.0% CS-001                                                                          3.51E-04  -5%    3.82E-04  -1%                                         (Roll #6)                                                                     __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: Room % RH                                                        Environment: Room % RH                                                                                       Naphtha %                                                       Aromatic      Improvement                                    Sample Identification                                                                          Transmission Rate*                                                                          Over Control                                   __________________________________________________________________________    Control Film (Roll #1)                                                                         7.81E-03      0%                                             0.5% CS-001 (Roll #7)                                                                          7.67E-03      2%                                             1% CS-001 (Roll #5)                                                                            7.37E-03      6%                                             2% CS-001 (Roll #8)                                                                            6.53E-03      16%                                            __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: Room % RH                                                        Environment: Room % RH                                                                         Aromatics %      Tot. Volitiles %                            Sample Aromatic  Improvement                                                                          Total Volitiles                                                                         Improvement                                 Identification                                                                       Transmission Rate*                                                                      Over Control                                                                         Transmission Rate*                                                                      Over Control                                __________________________________________________________________________    Control Film                                                                         5.16E-04   0%    5.63E-04  0%                                          1.0% CS-001                                                                          4.01E-04  22%    5.17E-04  8%                                          (Roll #5)                                                                     2.0% CS-001                                                                          2.91E-04  44%    3.08E-04  45%                                         (Roll #8)                                                                     __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: Room % RH                                                        Environment: Room % RH                                                                                       Naphtha %                                                       Aromatic      Improvement                                    Sample Identification                                                                          Transmission Rate*                                                                          Over Control                                   __________________________________________________________________________    Control Film (Roll #1)                                                                         7.81E-03      0%                                             0.5% CS-001 (Roll #7)                                                                          7.67E-03      2%                                             1% CS-001 (Roll #5)                                                                            7.37E-03      6%                                             2% CS-001 (Roll #8)                                                                            6.53E-03      16%                                            __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: 0.25 Aw                                                          Environment: 60% RH                                                                            Aromatics %      T. Volitiles %                              Sample Aromatic  Improvement                                                                          Total Volitiles                                                                         Improvement                                 Identification                                                                       Transmission Rate*                                                                      Over Control                                                                         Transmission Rate*                                                                      Over Control                                __________________________________________________________________________    Control Film                                                                         3.76E-04   0%    3.75E-04   0%                                         (Roll #1)                                                                     0.5% CS-001                                                                          2.42E-04  36%    2.41E-04  36%                                         (Roll #7)                                                                     1% CS-001                                                                            3.39E-04  10%    3.38E-04  10%                                         (Roll #5)                                                                     2% CS-001                                                                            2.48E-04  34%    2.47E-04  34%                                         (Roll #8)                                                                     __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: 0.25 Aw                                                          Environment: 60% RH                                                                            Aromatics %      T. Volitiles %                              Sample Aromatic  Improvement                                                                          Total Volitiles                                                                         Improvement                                 Identification                                                                       Transmission Rate*                                                                      Over Control                                                                         Transmission Rate*                                                                      Over Control                                __________________________________________________________________________    Control Film                                                                         1.03E-03   0%    1.13E-03   0%                                         (Roll #1)                                                                     1% CS-001                                                                            5.49E-04  47%    5.79E-04  49%                                         (Roll #2                                                                      1% CS-001                                                                            4.74E-04  54%    5.00E-04  56%                                         (Roll #3)                                                                     1% CS-001                                                                            6.41E-04  38%    6.83E-04  40%                                         (Roll #4)                                                                     1% CS-001                                                                            5.22E-04  49%    5.54E-04  51%                                         (Roll #5)                                                                     1% CS-001                                                                            4.13E-04  60%    4.39E-04  61%                                         (Roll #6)                                                                     2% CS-001                                                                            5.95E-04  42%    6.18E-04  45%                                         (Roll #8)                                                                     1% TMSE                                                                              8.32E-04  19%    8.93E-04  21%                                         (Roll #12)                                                                    __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 105° F.                                                    Sample Side: Room % RH                                                        Environment: Room % RH                                                                         Aromatics %      T. Volitiles %                              Sample Aromatic  Improvement                                                                          Total Volitiles                                                                         Improvement                                 Identification                                                                       Transmission Rate*                                                                      Over Control                                                                         Transmission Rate*                                                                      Over Control                                __________________________________________________________________________    Control Film                                                                         4.34E-04  0%     4.67E-04  0%                                          (Roll #1)                                                                     0.5% CS-001                                                                          4.03E-04  7%     4.41E-04  6%                                          (Roll #7)                                                                     1.0% CS-001                                                                          5.00E-04  -15%   5.33E-04  -14%                                        (Roll #5)                                                                     2.0% CS-001                                                                          3.96E-04  9%     3.94E-04  16%                                         (Roll #8)                                                                     __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: Room % RH                                                        Environment: Room % RH                                                                         Aromatics %      T. Volitiles %                              Sample Aromatic  Improvement                                                                          Total Volitiles                                                                         Improvement                                 Identification                                                                       Transmission Rate*                                                                      Over Control                                                                         Transmission Rate*                                                                      Over Control                                __________________________________________________________________________    Control Film                                                                         3.09E-04   0%    3.45E-04   0%                                         0.5% TMSE                                                                            2.50E-04  19%    2.96E-04  14%                                         (Roll #13)                                                                    0.5% TMSE                                                                            2.37E-04  23%    2.67E-04  33%                                         (Roll #14)                                                                    1% TMSE                                                                              2.67E-04  14%    3.05E-04  12%                                         (Roll #9)                                                                     1% TMSE                                                                              4.85E-04  -57%   5.27E-04  -53%                                        (Roll #10)                                                                    1% TMSE                                                                              2.58E-04  17%    2.92E-04  15%                                         (Roll #11)                                                                    1% TMSE                                                                              2.15E-04  31%    2.55E-04  26%                                         (Roll #12)                                                                    2% TMSE                                                                              2.54E-04  18%    3.04E-04  12%                                         (Roll #15)                                                                    2% TMSE                                                                              2.79E-04  10%    3.21E-04   7%                                         (Roll #16)                                                                    2% TMSE                                                                              2.81E-04   9%    3.24E-04   6%                                         (Roll #17)                                                                    __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: Room % RH                                                        Environment: Room % RH                                                                                       Naphtha %                                                       Aromatic      Improvement                                    Sample Identification                                                                          Transmission Rate*                                                                          Over Control                                   __________________________________________________________________________    Control Film (Roll #1)                                                                         9.43E-03        0%                                           1% TMSE (Roll #12)                                                                             1.16E-02      -23%                                           2% TMSE (Roll #15)                                                                             1.56E-02      -65%                                           __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: Room % RH                                                        Environment: Room % RH                                                                         Aromatics %      T. Volitiles %                              Sample Aromatic  Improvement                                                                          Total Volitiles                                                                         Improvement                                 Identification                                                                       Transmission Rate*                                                                      Over Control                                                                         Transmission Rate*                                                                      Over Control                                __________________________________________________________________________    Control Film                                                                         8.36E-04   0%    9.05E-04   0%                                         (Roll #1)                                                                     0.5% TMSE                                                                            6.77E-04  19%    7.25E-04  20%                                         (Roll #14)                                                                    2% TMSE                                                                              6.36E-04  24%    6.81E-04  25%                                         (Roll #15)                                                                    __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: 0.25 Aw                                                          Environment: 60% RH                                                                            Aromatics %      T. Volitiles %                              Sample Aromatic  Improvement                                                                          Total Volitiles                                                                         Improvement                                 Identification                                                                       Transmission Rate*                                                                      Over Control                                                                         Transmission Rate*                                                                      Over Control                                __________________________________________________________________________    PVdC   6.81E-05   0%    1.05E-04   0%                                         Control                                                                       PVdC w/                                                                              1.45E-05  79%    2.39E-05  77%                                         10% HP                                                                        B-CyD                                                                         PVdC w/                                                                              9.71E-05  -42%   1.12E-04  -7%                                         20% HP                                                                        B-CyD                                                                         __________________________________________________________________________    Comparison of Transmission Rates in                                           Modified β-Cyclodextrin - LPDE Films                                     Temperature 72° F.                                                     Sample Side: Room % RH                                                        Environment: Room % RH                                                                         Aromatics %      T. Volitiles %                              Sample Aromatic  Improvement                                                                          Total Volitiles                                                                         Improvement                                 Identification                                                                       Transmission Rate*                                                                      Over Control                                                                         Transmission Rate*                                                                      Over Control                                __________________________________________________________________________    Control                                                                              2.07E-06   0%    2.10E-05  0%                                          Acrylic                                                                       5% HP  1.50E-06  27%    2.07E-05  1%                                          B-CyD/                                                                        Acrylic                                                                       10% HP 4.13E-06  -100%  4.30E-05  -105%                                       B-CyD/                                                                        Acrylic                                                                       __________________________________________________________________________     *gm · 0.001 in. 100 in.sup.2 · 24 hrs.                 

We prepared a series of aqueous coatings containing hydroxypropyl βCD.One of the coatings was prepared from a 10% acrylic emulsion (apolyacrylic acid polymer having a molecular weight of about 150,000purchased from Polysciences, Inc.). The 10% acrylic emulsion containedhydroxypropyl βCD at a 5% and 10% by weight loading. These solutionswere used to hand-coat test film samples by laminating two films. Thecoatings were applied to linear low density polyethylene film sheetcontaining 0.5% acetylated βCD (Roll No. 7) and to a second film sheetcontaining 2% acetylated βCD (Roll No. 8) using a hand roller and thenlaminating the films. The films were not stretched during lamination.All coated samples were placed in a vacuum laminating press to removeair bubbles between the film sheets. The acrylic coating thickness wasabout 0.0002 inch. An acrylic coated control was prepared in anidentical manner containing no hydroxypropyl βCD. The multilayerstructure was tested with the 0.5% acetylated βCD film facing theenvironmental flask side of the test cell (FIG. 3).

A second coating was prepared from a vinylidene chloride latex (PVDC, 60wt-% solids) purchased from Dagax Laboratories, Inc. The PVDC latexcoating was prepared with two levels of hydroxypropyl βCD--10% and 20%by weight of the derivatized cyctodextrin. These solutions were used tohand-coat linear low density polyethylene test film samples bylaminating the two films together. The coatings were applied to twocontrol film sheets (rolled into one) using a hand roller and laminatedtogether. The films were not stretched during lamination process. Allcoated samples were placed in a vacuum laminating press to remove airbubbles between the film sheets. The PVDC coating thickness wasapproximately 0.0004 inch. A PVDC coated control was prepared in anidentical manner but without hydroxypropyl βCD.

The data following the preparatory examples showing improvement intransmission rate was obtained using the following general test method.

Method Summary

This method involves experimental techniques designed to measure thepermeability of selected organic molecules through food packaging films,using a static concentration gradient. The test methodology simulatesaccelerated shelf-life testing conditions by implementing variousstorage humidities, product water activities and temperature conditionsand using organic molecule concentrations found in previously testedfood products to simulate outside-the-package organic vapors in thepermeation test cell. This procedure allows for the determination of thefollowing compounds: ethanol, toluene, p-xylene, o-xylene,1,2,4-trimethyl benzene, naphthalene, naphtha solvent blend, etc.

    ______________________________________                                                         Threshold Environmental                                                       Odor Conc.                                                                              Cell Conc.                                         Test Compounds   ul/L ppm  ul/L ppm                                           ______________________________________                                        Ethanol             5-5000 20                                                 Toluene          0.10-20   3                                                  p-Xylene         0.5       2                                                  o-Xylene         0.03-12   1                                                  1,2,3-Trimethyl Benzene                                                                        NA        0.5                                                Naphthalene       0.001-0.03                                                                             0.5                                                Naphtha Solvent Blend                                                                          NA        40                                                 ______________________________________                                    

Table 1. Permeant Test Compounds

In a typical permeation experiment, three steps are involved. They are(a) the instrument sensitivity calibration, (b) film testing to measuretransmission and diffusion rates, and (c) the quality control of thepermeation experiment.

Film samples are tested in a closed volume permeation device.High-resolution gas chromatograph (HRGC) operated with a flameionization detector (FID) is used to measure the change in thecumulative penetrant concentration as a function of time.

Sample-side and environment-side test compound concentrations arecalculated from each compound's response factor or calibration curve.Concentrations are then volume-corrected for each specific set ofpermeation cells if permeant mass is desired.

The cumulative penetrant concentration is plotted as a function of timeon both the upstream (environment) and downstream (sample) side of thefilm. The diffusion rate and transmission rate of the permeant arecalculated from the permeation curve data.

1.0 Equipment and Reagents

2.1 Equipment

Gas chromatograph (HP 5880) equipped with flame ionization detector, asix-port heated sampling valve with 1 ml sampling loop and dataintegrator

J&W capillary column. DB-5, 30M×0.250 mm ID, 1.0 umdf.

Glass permeation test cells or flasks. Two glass flasks with cavities ofapproximately 1200 ml (environment cell or feed side) and 300 ml (sampleflask or permeating side) (FIG. 3).

Permeation cell clamping rings (2).

Permeation cell aluminum seal rings (2).

Natural Rubber Septa. 8 mm OD standard-wall or 9 mm OD (Aldrich ChemicalCompany, Milwaukee, Wis.).

Assorted laboratory glass ware and syringes.

Assorted laboratory supplies.

2.2 Reagents

Reagent water. Water in which interferences are not observed at the MDLof the chemical analytes of interest. A water purification system isused to generate reagent water which has been boiled to 80% volume,capped, and allowed to cool to room temperature before use.

Stock Ethanol/Aromatic Standard solution. Ethanol (0.6030 gram), toluene(0.1722 gram), p-xylene (0.1327 gram), o-xylene (0.0666 gram),trimethylbenzene (0.0375 gram) and naphthalene (0.0400 gram) package in1 ml sealed glass ampules. Naphtha blends standard is a commercial paintsolvent blend containing approximately twenty (20) individual aliphatichydrocarbon compounds obtained from Sunnyside Corporation, ConsumerProducts Division, Wheeling, Ill.

Triton X-100. Nonylphenol nonionic surface active agent (Rohm and Hass).

2.0 Standards Preparation

2.2 Permeation Working Standard

A stock permeant test standard solution is used. These standards areprepared by weight from neat certified reference compounds, actualweight and weight percent are shown.

The working ethanol/aromatic standard is prepared by injecting 250 ul ofthe stock standard solution into 100 ml of reagent water containing 0.1gram of surfactant (Triton X-100). It is important that the Triton X-100is completely dissolved in the reagent water prior to adding thepermeant stock standard. This will insure dispersing the test compoundsin the water. In addition, the working standard should be mixedthoroughly each time an aliquot is dispensed. It is advisable totransfer the working standard to crimp-top vials with no headspace tominimize losses due to the large headspace in the volumetric flask usedto prepare the standard.

A working naphtha blend standard is prepared by injecting 800 μL of the"neat" naphtha solvent blend into 100 milliliters of reagent watercontaining 0.2 gram of surfactant (Triton X-100).

An opened stock standard solution should be transferred from the glasssnap-cap vial to a crimp-top vial for short-term storage. The vials maybe stored in an explosion-proof refrigerator or freezer.

2.1 Calibration Standards

Calibration standards are prepared at a minimum of three concentrationlevels by adding volumes of the working standard to a volumetric flaskand diluting to volume with reagent water. One of the standards isprepared at a concentration near, but above, the method detection limit.The other concentrations correspond to the expected range ofconcentrations found in the environment and sample side cells.

3.0 Sample Preparation

3.1 Film Sample Preparation

The environment flask FIG. 3 and sample flask are washed before use insoapy water, thoroughly rinsed with deionized water, and oven-dried.Following cleaning, each flask is fitted with a rubber septum.

The film test specimen is cut to the inside diameter of the aluminumseal ring using a template. The film test specimen diameter is importantto prevent diffusion losses along the cut edge circumference. The filmsample, aluminum seals, and flasks are assembled as shown in FIG. 3, butthe clamping ring nuts are hot tightened.

The test cell (FIG. 3) is prepared. First the sample flask 32 andenvironment flask 31 are flushed with dry compressed air to removehumidity in the sample and environment flasks. This is done bypuncturing the sample system 33 and environment septum 34 with a needleand tubing assembly which permits a controlled flow of dry air throughboth flasks simultaneously. The clamp rings 35 are loosely fitted to theflasks to eliminate pressure buildup on either side of the film 30.After flushing both flasks for approximately 10 minutes, the needles areremoved and the clamp rings tightened, sealing the film 30 between thetwo flasks. Rubber faced aluminum spacers 36a, 36b are used to ensure agas tight fit.

The sample side is injected with 2 μL of water per 300 ml flask volume.Since the sample flasks vary in volume, the water is varied tocorrespond to the volume variations. The 2 μL of water in the 300 mlflask volume is comparable to a 0.25 water activity product at 72° F.Next, 40 μL, the permeation ethanol/aromatic working standard or 40 μLof the naphtha blend working standard prepared according to section 2.2,is injected into the environmental flask. Either of these workingstandards will produce a 60% relative humidity at 72° F. with a permeantconcentration (parts per million-volume/volume) in the 1200 ml volumeflask indicated in Table I. Other humidities or permeant concentrationsmay be employed in the test method by using psychrometric chart todetermine humidity and using the gas loss to calculate permeantconcentration. The time is recorded and the permeation cell placed intoa thermostatically controlled oven. Samples may be staggered toaccommodate GC run time. Three identical permeation devices areprepared. Triplicate analyses are used for QC purposes.

At the end of each time interval, a sample from the group is removedfrom the oven. The environmental flask is analyzed first, using a heatedsix-port sampling valve fitted with a 1 ml loop. The loop is flushedwith a 1 ml volume of the environment-side or sample-side air. The loopis injected onto the capillary column. The GC/FID system is startedmanually following the injection. Up to eight 1 ml sample injections maybe taken from the sample and environment side of a single permeationexperiment.

Sample side and environment side test compound concentrations arecalculated from each compound's calibration curve or response factor(equation 1 or 3). Concentrations are then volume-corrected for eachspecific set of permeation flasks if permeant mass is desired.

4.0 Sample Analysis

4.1 Instrument Parameters

Standards and samples-are analyzed by gas chromatography using thefollowing method parameters:

Column: J&W column, DB-5, 30M, 0.25 mm ID, 1 umdf

Carrier: Hydrogen

Split Vent: 9.4 ml/min

Injection Port Temp: 105° C.

Flame Detector Temp: 200° C.

Oven Temp 1: 75° C.

Program Rate1: 15° C.

Oven Temp 2: 125° C.

Rate 2: 20° C.

Final Oven Temp: 200° C.

Final Hold Time: 2 Min

The six-port sampling valve temperature is set to 105° C.

4.2 Calibration

A three point calibration is prepared using standards in the range ofthe following test compounds:

    ______________________________________                                                          Calibration                                                                   Curve Range                                                 Test Compounds    ppm (μL)                                                 ______________________________________                                        Ethanol             2-20                                                      Toluene           0.3-3                                                       p-Xylene          0.2-2                                                       o-Xylene          0.1-1                                                       1,2,4-Trimethyl Benzene                                                                          0.05-0.5                                                   Naphthalene        0.05-0.5                                                   Naphtha Solvent Blend                                                                            4.0-40                                                     ______________________________________                                    

To prepare a calibration standard, add an appropriate volume of theworking standard solution to an aliquot of reagent water in a volumetricflask.

4.2.1 Secondary Dilutions of Working Standard for Calibration Curve

5 to 1 dilution: Place 5 ml of working standard into a 25-ml volumetricflask, stopper, then mix by inverting flask.

2.5 to 1 dilution: Place 10 ml of working standard into a 25-mlvolumetric flask, stopper, then mix by inverting flask.

Analyze each calibration standard and tabulate compound peak arearesponse versus the concentration of the test compound in theenvironment side cell. The results are used to prepare a calibrationcurve for each compound. The naphtha solvent blend is a commercial paintsolvent containing approximately twenty (20) individual aliphatichydrocarbon compounds. The response versus concentration is determinedby totaling the area under each of the twenty individual peaks. Methodof least squares is used to fit a straight line to the calibrationcurve. The slope of each test compound's calibration curve is thencalculated for determining the unknown concentration. The averageresponse factor may be used in place of the calibration curve.

The working calibration curve or response factor must be verified oneach working day by measurement of one or more calibration standards. Ifthe response of any compound varies more than 20%, the test must berepeated using a fresh calibration standard. If the results still do notagree, generate a new calibration curve.

4.3 Analysis of Calibration Curve and Method Detection Level Samples

Recommended chromatographic conditions are summarized above.

Calibrate the system daily as described above.

Check and adjust split vent rate and check rate with soap film flowmeter.

To generate accurate data, samples, calibration standards and methoddetection level samples must be analyzed under identical conditions.

Calibration standards and method detection samples are prepared in theenvironment flask only. This is accomplished by using a 1/2 inch plasticdisk and aluminum sheet disk the diameter of the environment flange inplace of the sample flask. A single sealing ring is placed onto theenvironmental glass flange followed by an aluminum sheet, and then theplastic disk.

The environment flask is flushed with dry compressed air to removehumidity in the sample and environment flask. This is done by puncturingthe environment septa with a needle and tubing assembly which permits acontrolled flow of dry air through the flask. The clamp rings areloosely fitted to the flask to eliminate pressure buildup. Afterflushing both flasks for approximately 10 minutes, the needle is removedand the clamp rings tightened, sealing the aluminum sheet against theseal ring.

Next,40 μl of the permeation ethanol/aromatic working standard orsecondary dilutions of the working standard is injected into theenvironment flask. Alternatively, 40 μL of the naphtha solvent blend orsecondary dilutions of the working standard is injected into theenvironmental flask. The time is recorded and the flask is placed into athermostatically controlled oven.

At the end of 30 minutes, the environment flask is removed from theoven. The environmental flask is analyzed using a heated six-portsampling valve fitted with a 1 ml loop. The loop is flushed with a 1 mlvolume of the environment-side or sample-side air. The loop is injectedonto the capillary column. The GC/FID system is started manuallyfollowing the injection.

4.4 Calculation of Results

4.4.1 Test Compound Response Factor

Sample-side and environment-side test compound concentrations arecalculated for each compound's calibration curve slope or responsefactor (RF). Concentrations are then volume-corrected for each specificset of permeation cells if permeant mass is desired. ##EQU1##

The cumulative penetrant mass is plotted as a function of time on boththe upstream (environment) and downstream (sample) side of the film. Thediffusion rate and transmission rate of the permeant area calculatedfrom the transmission curve data.

4.4.2 Transmission Rate

When a permeant does not interact with the polymer, the permeabilitycoefficient, R, is usually characteristic for the permeant-polymersystem. This is the case with the permeation of many gases, such ashydrogen, nitrogen, oxygen, and carbon dioxide, through many polymers.If a permeant interacts with polymer molecules, as is the case with thepermeant test compounds used in this method, P is no longer constant andmay depend on the pressure, film thickness, and other conditions. Insuch cases, a single value of P does not represent the characteristicpermeability of the polymer membrane and it is necessary to know thedependency of P on all possible variables in order to obtain thecomplete profile of the permeability of the polymer. In these cases, thetransmission rate, Q, is often used for practical purposes, when thesaturated vapor pressure of the permeant at a specified temperature isapplied across the film. Permeability of films to water and organiccompounds is often expressed this way. ##EQU2##

One of the major variables in determining the permeation coefficient isthe pressure drop across the film. Since the transmission rate Qincludes neither pressure nor concentration of the permeant in itsdimensions, it is necessary to know either vapor pressure 15 or theconcentration of permeant under the conditions of the measurement inorder to correlate Q to P.

The pressure-drop across the film from environment side to sample sideis principally due to water vapor pressure. The water concentration orhumidity does not remain constant and is not measured during the timeintervals the organic compounds are analyzed, and therefore the pressureacross the membrane is not determined.

The above examples of thermoplastic films containing a variety ofcompatible cyclodextrin derivatives shows that the invention can beembodied in a variety of different thermoplastic films. Further, avariety of different compatible derivatized cyclodextrin materials canbe used in the invention. Lastly, the films can be manufactured using avariety of film manufacturing techniques including extrusion and aqueousdispersion coating to produce useful barriers.

The above specification, examples of substituted cyclodextrin, extrudedthermoplastic films and test data provide a basis for understanding thetechnical aspects of the invention. Since the invention can be made witha variety of embodiments, the invention resides in the claimshereinafter appended.

We claim:
 1. A method to prevent moisture vapor transmission to an item which method comprises separating the item from a source of moisture by imposing a thermoplastic film barrier between the source of moisture and the item, the film barrier comprising:(a) a thermoplastic polymer; and (b) uniformly dispersed in the polymer, an effective permeant absorbing amount of a modified cyclodextrin having pendent moieties or substituents that render the cyclodextrin compatible with the thermoplastic polymer;wherein the cyclodextrin is substantially free of an inclusion complex compound.
 2. The method of claim 1 wherein the thermoplastic polymer comprises a vinyl polymer comprising an alpha-olefin.
 3. The method of claim 1 wherein the thermoplastic polymer comprises a chlorine containing vinyl polymer comprising vinyl chloride or vinylidene chloride.
 4. The method of claim 3 wherein the thermoplastic polymer comprises a poly(vinyl chloride-co-vinyl acetate) or a poly(vinyl chloride-co-vinylidene chloride).
 5. The method of claim 2 wherein the thermoplastic polymer comprises a polyvinylalcohol, poly (ethylene-co-vinyl alcohol), a polyethylene-co-methyl acrylate).
 6. The method of claim 1 wherein the cyclodextrin derivative comprises a β-cyclodextrin derivative.
 7. The method of claim 1 wherein the modified cyclodextrin contains at least one substituent on a cyclodextrin primary carbon atom.
 8. The method of claim 1 wherein the modified cyclodextrin comprises a modified a-cyclodextrin, b-cyclodextrin, g-cyclodextrin or mixtures thereof.
 9. The method of claim 1 wherein the thermoplastic polymer contains about 0.1 to 5 wt-% of the modified cyclodextrin.
 10. A method to prevent contamination of a food item by a hydrocarbon vapor which method comprises separating the food item from a source of the hydrocarbon by imposing a thermoplastic film barrier between the source of hydrocarbon and the food item, the film barrier comprising:(a) a thermoplastic polymer; and (b) uniformly dispersed in the polymer, an effective permeant absorbing amount of a modified cyclodextrin having pendent moieties or substituents that render the cyclodextrin compatible with the thermoplastic polymer;wherein the cyclodextrin is substantially free of an inclusion complex compound.
 11. The method of claim 10 wherein the thermoplastic polymer comprises a vinyl polymer comprising an alpha-olefin.
 12. The method of claim 10 wherein the thermoplastic polymer comprises a chlorine containing vinyl polymer comprising vinyl chloride or vinylidene dichloride.
 13. The method of claim 12 wherein the thermoplastic polymer comprises a poly(vinyl chloride-co-vinyl acetate) or a poly(vinyl chloride-co-vinylidene dichloride).
 14. The method of claim 11 wherein the thermoplastic polymer comprises a polyvinylalcohol, poly(ethylene-covinyl alcohol) or a polyethylene-co-methyl acrylate).
 15. The method of claim 10 wherein the modified cyclodextrin comprises a modified b-cyclodextrin.
 16. The method of claim 10 wherein the modified cyclodextrin contains at least one substituent on a cyclodextrin primary carbon atom.
 17. The method of claim 10 wherein the modified cyclodextrin comprises a modified a-cyclodextrin, b-cyclodextrin, g-cyclodextrin or mixtures thereof.
 18. The method of claim 10 wherein the thermoplastic polymer contains about 0.1 to 5 wt-% of the modified cyclodextrin.
 19. A method to prevent contamination of a food item by a fragrance, which method comprises separating the food item from a source of the fragrance by imposing a thermoplastic film barrier between the food item and the source of fragrance, the film barrier comprising:(a) a thermoplastic polymer; and (b) a uniformly dispersed in the polymer, an effective fragrance permeant absorbing amount of a modified cyclodextrin having pendent moieties or substituents that render the cyclodextrin compatible with the thermoplastic polymer;wherein the cyclodextrin is substantially free of an inclusion complex compound.
 20. The method of claim 19 wherein the thermoplastic polymer comprises a vinyl polymer comprising an alpha-olefin.
 21. The method of claim 19 wherein the thermoplastic polymer comprises a chlorine containing vinyl polymer comprising vinyl chloride or vinylidene dichloride.
 22. The method of claim 21 wherein the thermoplastic polymer comprises a poly(vinyl chloride-co-vinyl acetate) or a poly(vinyl chloride-co-vinylidene dichloride).
 23. The method of claim 20 wherein the thermoplastic polymer comprises a polyvinylalcohol, poly (ethylene-co-vinyl alcohol), a poly (ethylene-co-methyl acrylate).
 24. The method of claim 19 wherein the modified cyclodextrin comprises a modified b-cyclodextrin.
 25. The method of claim 19 wherein the modified cyclodextrin contains at least one substituent on a cyclodextrin primary carbon atom.
 26. The method of claim 19 wherein the modified cyclodextrin comprises a modified a-cyclodextrin, b-cyclodextrin, g-cyclodextrin, or mixtures thereof.
 27. The method of claim 19 wherein the thermoplastic polymer contains about 0.1 to about 5 wt-% of the modified cyclodextrin.
 28. A method for preventing release of a pest attracting aroma from a food item comprising a meat product or a food product containing a cocoa derivative which method comprises imposing a barrier between the food item and the environment effective to prevent the release of a pest attracting aroma, said barrier comprising:(a) a thermoplastic polymer; and (b) uniformly dispersed in the polymer, an effective aroma permeant absorbing amount of a modified cyclodextrin having pendent moieties or substituents that render the cyclodextrin compatible with the thermoplastic polymer;wherein the cyclodextrin is substantially free of an inclusion complex compound.
 29. The method of claim 28 wherein the thermoplastic polymer comprises a vinyl polymer comprising an alpha-olefin.
 30. The method of claim 28 wherein the thermoplastic polymer comprises a chlorine containing vinyl polymer comprising vinyl chloride or vinylidene chloride.
 31. The method of claim 30 wherein the thermoplastic polymer comprises a poly(vinyl chloride-co-vinyl acetate) or a poly(vinyl chloride-co-vinylidene chloride).
 32. The method of claim 29 wherein the thermoplastic polymer comprises a polyvinylalcohol, poly (ethylene-co-vinyl alcohol), a poly(ethylene-co-methyl acrylate).
 33. The method of claim 28 wherein the modified cyclodextrin comprises a modified b-cyclodextrin.
 34. The method of claim 28 wherein the modified cyclodextrin contains at least one substituent on a cyclodextrin primary carbon atom.
 35. The method of claim 28 wherein the modified cyclodextrin comprises a modified a-cyclodextrin, b-cyclodextrin, g-cyclodextrin, or mixtures thereof.
 36. The method of claim 28 wherein the thermoplastic contains about 0.1 to about 5 wt-% of the modified cyclodextrin. 